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src/Framebuffer.c  view on Meta::CPAN

                    if (col8 != 0) res8 = fb / col8;
                    break;
                default:
                    break;
            }
            *p = res8;
        } break;

        case 1: {
            /* Not supported yet; no-op */
        } break;

        default:
            break;
    }
}

/* Draws a line */
void c_line(char *framebuffer,
            short x1,
            short y1,
            short x2,
            short y2,
            short x_clip,
            short y_clip,
            short xx_clip,
            short yy_clip,
            unsigned int color,
            unsigned int bcolor,
            unsigned char alpha,
            unsigned char draw_mode,
            unsigned char bytes_per_pixel,
            unsigned char bits_per_pixel,
            unsigned int bytes_per_line,
            short xoffset,
            short yoffset,
            bool antialiased) {
    /* If antialiasing is requested, use Xiaolin Wu's algorithm... */
    if (antialiased) {
        double x0 = (double)x1;
        double y0 = (double)y1;
        double x1d = (double)x2;
        double y1d = (double)y2;

        int steep = fabs(y1d - y0) > fabs(x1d - x0);

        if (steep) {
            swap_(x0, y0);
            swap_(x1d, y1d);
        }

        if (x0 > x1d) {
            swap_(x0, x1d);
            swap_(y0, y1d);
        }

        double dx = x1d - x0;
        double dy = y1d - y0;
        double gradient = (dx == 0.0) ? 1.0 : dy / dx;

        /* handle first endpoint */
        double xend = roundd(x0);
        double yend = y0 + gradient * (xend - x0);
        double xgap = rfpart(x0 + 0.5);
        long xpxl1 = (long)xend;
        long ypxl1 = (long)floor(yend);

        /* plot first endpoint */
        double intery = yend + gradient; /* first y-intersection for the main loop */

        /* First endpoint pixels */
        plot_aa_pixel(framebuffer,
                      color,
                      bcolor,
                      alpha,
                      bytes_per_pixel,
                      bits_per_pixel,
                      bytes_per_line,
                      x_clip,
                      y_clip,
                      xx_clip,
                      yy_clip,
                      xoffset,
                      yoffset,
                      steep,
                      xpxl1,
                      ypxl1,
                      rfpart(yend) * xgap);
        plot_aa_pixel(framebuffer,
                      color,
                      bcolor,
                      alpha,
                      bytes_per_pixel,
                      bits_per_pixel,
                      bytes_per_line,
                      x_clip,
                      y_clip,
                      xx_clip,
                      yy_clip,
                      xoffset,
                      yoffset,
                      steep,
                      xpxl1,
                      ypxl1 + 1,
                      fpart(yend) * xgap);

        /* handle second endpoint */
        xend = roundd(x1d);
        yend = y1d + gradient * (xend - x1d);
        xgap = fpart(x1d + 0.5);
        long xpxl2 = (long)xend;
        long ypxl2 = (long)floor(yend);

        plot_aa_pixel(framebuffer,
                      color,
                      bcolor,
                      alpha,
                      bytes_per_pixel,
                      bits_per_pixel,
                      bytes_per_line,
                      x_clip,
                      y_clip,
                      xx_clip,
                      yy_clip,
                      xoffset,
                      yoffset,
                      steep,
                      xpxl2,
                      ypxl2,
                      rfpart(yend) * xgap);
        plot_aa_pixel(framebuffer,
                      color,
                      bcolor,
                      alpha,
                      bytes_per_pixel,
                      bits_per_pixel,
                      bytes_per_line,
                      x_clip,
                      y_clip,
                      xx_clip,
                      yy_clip,
                      xoffset,
                      yoffset,
                      steep,
                      xpxl2,
                      ypxl2 + 1,
                      fpart(yend) * xgap);

        /* main loop */
        long x;
        if (xpxl1 + 1 <= xpxl2 - 1) {
            for (x = xpxl1 + 1; x <= xpxl2 - 1; x++) {
                double iy = intery;
                long yint = (long)floor(iy);
                plot_aa_pixel(framebuffer,
                              color,
                              bcolor,
                              alpha,
                              bytes_per_pixel,
                              bits_per_pixel,
                              bytes_per_line,
                              x_clip,
                              y_clip,
                              xx_clip,
                              yy_clip,
                              xoffset,
                              yoffset,